The stock Dana 30/44 combo that comes on an LJ won't hold up to 37s. The biggest issue is that the stock Dana 30 outer balljoints on the front are too weak. There's enough examples of even heavily built Dana JK 44s will wear out the internals over time if ran offroad. So for axles I decided on Dana 60s. Currie makes their version, the RockJock 60, which main advantage is that the ground clearance is higher than your junkyard 60s. Along with some other improvements Currie added which are great for offroading, which I'll go over, they were also able to build to my specs which saves me a lot of time vs piecing together my own from a junkyard.
A lot of planning went into speccing the axles to be just right for my build. It took about 2 months to get everything right on paper before giving Currie the go ahead. (As a side note, if anyone is wanting to repeat my order, make sure you buy through a reputable reseller as some of the discount resellers may not be worth the savings you receive. I purchased through Ricky at 4LowParts and he has been very helpful and had no issue putting together my order. He answered all of my questions without making me feel like I was wasting his time.)
Starting at the differentials, the RJ60VXR are a high pinion design, which results in the pinion running on the weak side of the ring gear teeth in the rear, this can cause the ring gear to deflect under high load and skip teeth. I upgraded to the RJ60VXR diff housing for the front and rear. The VXR housing adds a few benefits but the main reason I went with it was for the load bolt to prevent ring gear deflection in the rear. I also went with Ford Super 60 gears which are larger diameter and thicker than the standard Dana 60 gears. I wanted to go with a lower gear ratio in the diffs like a 6.17 but the lowest Currie will go in their housings is a 5.38, so that's what I went with, we'll have to make up for it with the engine later. ARB lockers front and rear were chosen for their reliability and ability to provide expected behavior on snowy and icy roads.
The load bolt can be seen near the middle:
For the yoke, it is high pinion (HP) which will improve driveline angles and keep the yoke out of the rocks. I went with a 1310 yoke to allow for the maximum driveline angle when at full droop, to act as a fuse to prevent damage to the transfer case, and because it's simply strong enough to run even larger tires than I will be. There's simply no reason to go to a bigger ujoint.
The rear has a AR500 steel skid under the diff, the same material that bulldozer buckets are made from. It's strong and doesn't gouge and "grab" onto rocks like an aluminum skid would. For the front Currie forgot to include a skid but for now I won't be running one up there, Blaine mentioned that the fronts like to get caught on rocks and rip off anyway( which immediately made sense when I actually thought about it). Currie is sending a skid over if I later decide to put it on.
Because of the angle of the RockJock 60 covers they built in a dip stick to check fluid levels:
The VXR includes 3.5" .375" wall axle tubes. I omitted all of the brackets except for TJ lower control arm brackets and bridges. This will be correct for the 4 link rear and 3 link front. There is no room for coil buckets on the front at 65" WMS, even the driver's side LCA mount is partially frenched into the diff housing. Part of the reason why I'll need to go with coilovers.
RCV shafts were chosen for the front for their ability to give constant wheel speed in case I need to drive home across the country in front wheel drive after breaking something in the rear. I also have a theory that they may provide better handling on snowy roads while in 4wd since they won't break traction with every revolution. RCVs added strength and warranty is a cherry on top but not a reason for upgrading.
On the ends up front I went with a '04 Ford style balljoint design on the iron knuckles, the unit bearings are based on the F450 design and include a sane 5x5.5" bolt pattern with 1/2" studs. Front brakes will be later built by Black Magic Brakes. Yukon manual locking hubs will be used up front which are narrower and stronger than those from Warn.
The upper steering arms should have included a hole to be in shear with the lower steering arms but due to a recent change at Currie they are unable to provide those and a strange combo was sent to me instead. Currie is mailing me the correct blank steering arm design which I will be drilling to work with my custom crossover steering.
In the rear the simple option would have been to go with Explorer brakes flip the left to right to get the calipers to the front of the housings and call it a day. And that would have been fine and held up long term combined with the semifloat shafts. I wanted a 35 spline full float rear so I could drive home on a broken rear shaft if necessary and to further prevent deflection on the ring gear. The main contenders here were either expensive and complex designs made for Ultra4, full size truck brakes, or Currie's Wilwood brake kit. But I didn't want to compromise or run junk brakes. I ended up going with the Currie JK floater spindle (
https://www.currieenterprises.com/CE-0013JK5L). This full float design uses OEM JK brakes which are reliable, available, and they'll allow to me have the correct 75/25 braking ratio with the front without messing around with a proportioning valve. Awesome! With some ingenuity I should be able to make the parking brake connect up with the TJ cables. They are finished off with Currie drive flanges. Oh, and Currie welded the snouts to opposite sides for me so that there would be more room for coilovers in the rear by placing the calipers on the front!
The 3.5" tubes are sleeved down for the rear snouts and JK backing plates:
Pictures don't do these axles justice. They are large, beefy, and precise without being overkill.